Mannosidosis of Angus cattle is being studied as a model lysosomal storage disease with present emphasis on storage and excretion patterns of oligosaccharides and the underlying morphological basis of the neurological deficit. Major research emphasis is however on another storage-disease, ceroid-lipofuscinosis, whose pathogenesis is unknown and remains an enigma. A flock of sheep carrying this defect has now been developed to provide affected individuals. A herd of mannosidosis heterozygous cattle is likewise maintained and efforts are being made to establish a colony of dogs with Gaucher disease (glucocerebrosidosis). The objective has been, and remains, to define each model in depth in regard to pathology, pathogenesis, dynamics of storage and excretion of storage material and characteristics of the mutant enzyme. This is to help develop methods of precise early diagnosis, heterozygote detection and provide a basis for development of specific enzyme replacement or non-specific therapeutic strategies. In regard to the latter, some experiments may be designed on an organ rather than whole animal approach, so that specific questions are answered. Other models, if they are found, may be likewise developed and made available to other research workers. The investigative approach involves biochemical, electrophysiological and morphological studies. As our research has become broad based, we see collaborative studies as being of particular importance and in a number of instances collaboration (Appendix 1) has been arranged.